The invention relates to eggs and particularly, to the discovery of an improved composition and process which permit higher temperature processing with minimal denaturation. This enables both the production of a pasteurized egg product of improved functionality and a packaged egg product having improved stability during refrigerated storage.
Pasteurization has been employed to aid in the preservation of many food products, including eggs. Eggs are particularly susceptible to degradation during heating due to the nature of their protein content. Most commercial processes are employed primarily to reduce Salmonella to safe levels while bringing spoilage-promoting organisms to levels which typically permit one to two weeks stability at refrigerator temperatures (e.g., 32.degree. to 40.degree. F.). Until recently, aseptically-packaged, room-temperature stable eggs or refrigerator-stable eggs were not available on a commercial scale.
In an early advance in egg pasteurization, Lineweaver and Cunningham disclosed in U.S. Pat. No. 3,251,697 that the addition of certain polyvalent metal salts enabled increasing the pasteurization temperature several degrees while not adversely affecting the physical properties of the egg.
This process was confirmed as useful by Strong and Redfern in U.S. Pat. Nos. 3,840,683 and 3,911,144 wherein they disclosed a substantially cholesterol and egg yolk free liquid egg product which had good freeze-thaw stability. These technologies permitted the marketing and wide availability of a health-oriented product highly desired by many egg lovers. When frozen, the products would last for extended times. It would be desirable, however, to improve the stability of such products against spoilage once thawed, or if maintained in a refrigerated condition without freezing.
More recently, efforts have been made to produce products which remain stable for extended periods of refrigerated or even room-temperature storage. For example, in U.S. Pat. No. 3,928,632, Glaser and Ingerson disclosed an aseptically-packaged, low-cholesterol egg product having an additive emulsion which is separately sterilized and homogenized prior to mixing with an egg component. No details of egg pasteurization are provided, but a lactylate salt is an essential ingredient. It would be desirable to increase the acceptable pasteurization temperatures to achieve longer shelf lives with minimal equipment fouling.
Swartzel et al, in U.S. Pat. Nos. 4,808,425 and 4,957,759 disclose the ability to obtain a shelf-stable whole egg product by high-temperature, short-time ultrapasteurization of liquid whole egg combined with aseptic packaging. In European Patent Application 344,123 Maley et al point out that whole eggs can withstand temperatures about 20.degree. F. higher than egg white. Denaturation is preferably kept as low as possible. Similarly, in U.S. Pat. No. 4,971,827, Huang discloses that high temperatures can be employed when turbulent flow is achieved during pasteurization.
It would be advantageous to have an additive, formulation or procedure for assuring low degrees of denaturation with adequate heat treatment for preservation.